Method of producing carbon granules



paaren stars separat? @sans TERRENCE ONAS WESTEAFER, OF DOWNERS GROVE, ILLINOIlASSIGNOR TO WESTERN ELECTRIC COMPANY, INCORPORATED, 0F NEW YORK, N. Y., vA. CORPORATION 0F New vom METHOD OF PBOD'UOING CARBON GRANULES Application :tiled April 12,

This invention relaes to a method of producing carbon granules, and more particularly to a method of treating carbonizable material to form spherical carbon granules.

In variable resistance. units such as are used in sound translating devices of which a telephone transmitter is an example, the use of carbon 4particles of a' uniform size and of a spherical shape is very desirable in order to obtain uniform microphonic properties. In some instances where irregularly shaped particles have been used there is a tendency for the 4sharp points of the carbon to penetrate the thin walls ofthe container of the unit and thus cause a leakage of the carbon from the container, thereby impairing theeciency of the unit. In view of the fact that the individual spherical granule is quite small a large number of granules are required for a single resistance unit.

It is an object of this invention to provide a method by which large numbers of spherical carbon granules may be quickly and economically produced. I

In accordance with the eneral features of the invention, a stream or last of air is used to break the carbonizable material into a plurality of particles which are subjected to such conditions as will cause them to assume a spherical form, whereupon the particles are hardened and carbonized.

It is believed that a complete understanding of the invention may be had by reference to the following description, taken 1n conjunction with the accompanying drawings, in which Fig. 1 is an elevational view, partly in section, of an apparatus which is suitable for practicing the invention;

Fig. 2 1s an elevational View of a modified form of apparatus for practicing the invention, and

Fig. 3 is an elevational view of another form of apparatus for practicing the invention.`

Referring to the drawings, a tank 7 is shown containing a carbonizable liquid 8, which may consist of vegetable fibres or cellulose dissolved? in a solution of zinc chlor-ide or any other suitable carbonizable material ieee. serial No. 269,502.

such asis commonly used as lament stock for carbon filaments employed in incandescent lamps.

A tube 9 connects the tank 7 to any suitable air pressure system (not shown) for the purpose of expelling the carbonizable liquid from the tank. In the apparatus of Fig. 1, the carbonizable liquid passes from the tank 7 Vinto a tube 11 which conducts the liquid into a cylinder 12 having a reciprocable piston 413 therein. The piston 13 is provided with a tubular aperture, one end of which terminates 1n a cavity 14 under the piston and the other endterminates in the cylindrical wall of theV piston in such a position that it will coincide with the opening of a tube 15 from the pressure system when the pistonis in its lowermost position. l/Vhen the piston is reciprocated, the cavity 14 will alternately be connected with the tube 11 to supply a quantity of material to the cavity yand with the tube 15 to expel the material from the cavity by a blast ofv air. In this manner a particle of y ity of particles.

In Fig. 3 is shown an apparatus in which the material from the tank 7 is conducted through a tube 18 and deposited in a tube 19 from which it is expelled byv means of an in-'` termittent current of air. The tube 19 is connected to a pressure system' (not shown) and 1s provided with an intei'rupter 21 of any suitable type. The material expelled from the tube 19 may be intercepted by an inclined surface 22 from which the material drops by gravity in a plurality of small particles.

' The articles or pellets of carbonizable material t us formed, as described in connection with the diiierent apparatus, are deposited in an alcohol bath 23 in a long container 24 several feet in height which gives the pellets Leashes sucient time to solidify and harden before reachin the base of the container where they accumu ate and cornek in contact with one another. In the alcohol bath the pellets are reduced considerably in size and become sufciently hard to bear handling. The alcohol treatment im arts a tenacious outer skin to the pellets. Xfter the pellets have been retained in the alcohol 'a suflicient length of time they are removed and dried.

The cellulose pellets are carbonized by heating them in an inert atmosphere such as a hydrogen atmosphere which prevents oxidation of the material. The pellets are first heated to a comparatively low temperature for an-eXted-edperiod to'eXpel any volatile substance contained therein after which the temperature is raised suciently high to carbonize 'the material leaving it in the form of sphericalcarbon granules. f

It has been found that spherical carbon granules formed as described above are particularly Well adapted for use in sound transmitting devices having what is known as a floating diaphragm which is resiliently supported. The spherical granules have no appreciable tendency to work their way out of their containenthrough the juncture between the container and the diaphragm. When the spherical particles are used in variable resistance units very satisfactory results are also obtained due to the fact that the spherical granules can conveniently be made of a substantially uniform size and therefore a more uniform variation of the resistance will It will be understood that the illustration of the invention herein described is merelyy a convenient and useful form of the invention which is capable of many other modifications without departing from the spirit and scope of the invention,

What is claimed is:

A method of producing spherical carbon granules, which com rises projecting an aqueous solution of ce lulose and zinc chloride into the atmosphere so as to break it into a plurality of drops, depositin lthe dro l in a bath of'alcohol to harden the rops whl e their surface tension `draws them intos herical shape, and carbonizing the hardbned drops to form spherical carbon granules.

ln witness whereof, I hereunto subscribe my name this 29th dal of March, A. D., 1928.

'PERRENCE 0 AS WESTHAFER. 

